A young mother whose disappearance last month on the way home from a wedding in rural Oregon prompted a days-long search did not wander off but died instantly when she exited her mother's moving car, hit her head on a guardrail and slid down an embankment, a prosecutor said this week.

Meighan Cordie's body, hidden at the bottom of the steep slope, wasn't discovered until some joggers spotted it off the roadway four days after the Aug. 18 incident, Yamhill County District Attorney Brad Berry said at a news conference.

Cordie's mother is not being charged in her daughter's death but was cited for driving while intoxicated and reckless endangerment, he said. She has a court appearance next week.

The announcement provides the first public accounting of a bizarre disappearance that continued to baffle investigators even after Cordie's body was found.

Search crews scoured the rural area of agricultural fields for days, believing that Cordie had left her mother's car in anger during a fight on the way home from the wedding and walked into the dark alone without shoes or her cellphone.

But when found, Cordie's body showed signs of blunt force trauma. An autopsy subsequently revealed she had suffered an aortic separation, likely after her back hit the guard rail, and also had head trauma, Berry said.

The Oregon Medical Examiner's Office ruled the death accidental.

On Thursday, Berry described a complicated investigation that pieced together clues from the scene - including Cordie's hair found in the guard rail - cellphone records, lie detector tests and interviews with Cordie's 3-year-old daughter who was in the car and witnessed the incident.

Cordie's boyfriend overheard her fighting with her mother in a cellphone call that provided a narrow timeframe for the death, Berry said. And a clump of Cordie's mother's hair was found in the car, Berry said, indicating a violent altercation.

Investigators concluded the death was tragic, but was not a crime, he said.

"Every crime consists of elements," he said of the decision not to charge Cordie's mother. "We can prove elements of certain crimes (but) we just can't prove all of the elements of a single crime. Clearly leaving her daughter there, if we're talking right versus wrong, it's hard for me to fathom that somebody would do that - but it doesn't mean that I've got a crime."

Berry said Cordie and her mother had a "difficult" relationship and began arguing as they left the wedding.

The mother was intoxicated and wanted to stay longer, but Cordie wanted to get home because her young daughter was getting tired. Cordie got out of the car once, only to be coaxed back in by her mother.

Cordie then called her boyfriend and asked him to come get her.

Then, the evidence shows, she opened the car door and either fell or intentionally jumped from the moving car, Berry said. Cordie's young daughter told police her mother was in the backseat at the time.

The mother has not cooperated with authorities since taking an initial polygraph test and it's unclear if she realized her daughter had been killed, Berry said. The results of the test were inconclusive, he said.

She told investigators that she had looked for her daughter in the dark and then went home.